Functional or Vestigial? The Genomics of the Pineal Gland in Xenarthra

Valente, Raúl; Alves, Filipe; Sousa-Pinto, Isabel; Ruivo, Raquel; Castro, L. Filipe C.

doi:10.1007/s00239-021-10025-1

Cited by 7 publications

(4 citation statements)

References 78 publications

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“…Comparative genomics is a powerful tool to decipher the origin and loss of phenotypic variations (Huelsmann et al 2019 ; Zoonomia Consortium 2020 ; Alves et al 2021 ; Fuchs et al 2022 ; Zheng et al 2022 ). Specifically, gene loss-aware research is reverberating, highlighting the role of secondary losses in the emergence of diverse biological features, including the simplification of body plans (i.e., urochordates), the deconstruction of the vertebrate organs (i.e., stomach, pineal gland), the modulation of sensory acuity (i.e., vision, taste), or even behavior and locomotion (Castro et al 2014 ; Zhao et al 2015 ; Lopes-Marques et al 2019a , b ; Valente et al 2021a , b ; Carneiro et al 2021 ; Ferrández-Roldán et al 2021 ; Indrischek et al 2022 ).…”

Section: Resultsmentioning

confidence: 99%

Decay of Skin-Specific Gene Modules in Pangolins

et al. 2023

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The mammalian skin exhibits a rich spectrum of evolutionary adaptations. The pilosebaceous unit, composed of the hair shaft, follicle, and the sebaceous gland, is the most striking synapomorphy. The evolutionary diversification of mammals across different ecological niches was paralleled by the appearance of an ample variety of skin modifications. Pangolins, order Pholidota, exhibit keratin-derived scales, one of the most iconic skin appendages. This formidable armor is intended to serve as a deterrent against predators. Surprisingly, while pangolins have hair on their abdomens, the occurrence of sebaceous and sweat glands is contentious. Here, we explore various molecular modules of skin physiology in four pangolin genomes, including that of sebum production. We show that genes driving wax monoester formation, Awat1/2, show patterns of inactivation in the stem pangolin branch, while the triacylglycerol synthesis gene Dgat2l6 seems independently eroded in the African and Asian clades. In contrast, Elovl3 implicated in the formation of specific neutral lipids required for skin barrier function is intact and expressed in the pangolin skin. An extended comparative analysis shows that genes involved in skin pathogen defense and structural integrity of keratinocyte layers also show inactivating mutations: associated with both ancestral and independent pseudogenization events. Finally, we deduce that the suggested absence of sweat glands is not paralleled by the inactivation of the ATP-binding cassette transporter Abcc11, as previously described in Cetacea. Our findings reveal the sophisticated and complex history of gene retention and loss as key mechanisms in the evolution of the highly modified mammalian skin phenotypes.

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Section: Resultsmentioning

confidence: 99%

Decay of Skin-Specific Gene Modules in Pangolins

et al. 2023

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“…stomach, pineal gland), the modulation of sensorial acuity (i.e. vision, taste), or even behavior and locomotion (Castro et al 2013; Zhao et al 2015; Lopes-Marques et al 2019; Valente et al 2021; Carneiro et al 2021; Ferrández-Roldán et al 2021; Indrischek et al 2022).…”

Section: Resultsmentioning

confidence: 99%

Convergent Decay of Skin-specific Gene Modules in Pangolins

Pinto

Valente

Caramelo

et al. 2022

Preprint

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The Mammalia skin exhibits a rich spectrum of evolutionary adaptations. The pilosebaceous unit, composed of the hair shaft, follicle, and the sebaceous gland, is the most striking synapomorphy. The evolutionary diversification of mammals across different ecological niches was paralleled by the appearance of an ample variety of skin modifications. Pangolins, order Pholidota, exhibit keratin-derived scales, one of the most iconic skin appendages. This formidable armor is intended to serve as a key deterrent against predators. Surprisingly, while pangolins have hair on their abdomens, the occurrence of sebaceous and sweat glands is contentious. Here, we explore various molecular modules of skin physiology in four pangolin genomes, including that of sebum production. We show that genes driving wax monoester formation - Awat1/2, show patterns of inactivation in the stem pangolin branch; while the triacylglycerol synthesis gene Dgat2l6 seems independently eroded in the African and Asian clades. In contrast, Elovl3 implicated in the formation of specific neutral lipids required for skin barrier function, is intact and expressed in the skin. An extended comparative analysis shows that genes involved in skin pathogen defense and structural integrity of keratinocyte layers also show inactivating mutations: associated with both ancestral and independent pseudogenization events. Finally, we deduce that the suggested absence of sweat glands is not paralleled by the inactivation of the ATP-binding cassette transporter Abcc11, as previously described in Cetacea. Our findings reveal the sophisticated, convergent and complex history of gene retention and loss as key mechanisms in the evolution of the highly modified mammalian skin phenotypes

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“…The pineal gland is absent or non-functional in sirenians, cetaceans, and some terrestrial mammals. These species do not encode genes associated with the synthesis and reception of melatonin, a hormone essential for light stimulation of the circadian clock [50][51][52][53][54] . Sirenians do not show a 'classical' diel (24-hour) activity pattern, have unihemispheric slow wave sleep (i.e., one brain half is awake), and appear to respond behaviorally to tidal currents (tides may restrict foraging) and seasonal changes in water temperature 5,55,56 .…”

Section: Daily Activity Patternsmentioning

confidence: 99%

Sirenian genomes illuminate the evolution of fully aquatic species within the mammalian superorder Afrotheria

Tian,

Zhang,

Kang

et al. 2023

Preprint

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Sirenians of the diverse superorder Afrotheria were the first mammals to retransition from land to water and are the sole herbivorous marine mammals, but little is known about the underlying genomic changes. Here, we generated a chromosome-level dugong (Dugong dugon) genome. A comparison of our assembly and a recent West Indian manatee genome with other afrotherian genomes revealed possible molecular solutions to aquatic life by sirenians, including a shift in daily activity patterns (circadian clock) and tolerance to a high-iodine plant diet mediated through changes in the iodide transporter NIS (SLC5A5) and its co-transporters. Functional in vitro assays confirmed that sirenian amino acid substitutions alter the properties of the circadian clock protein PER2 and NIS. Sirenians show evidence of convergent regression of integumentary system (skin and its appendages) genes with cetaceans, the only other fully aquatic mammal group. Our analysis also uncovered gene losses that may be maladaptive in a modern environment, including a candidate gene (KCNK18) for sirenian cold stress syndrome likely lost during their evolutionary shift in daily activity patterns. Finally, genomes from nine Australian locations and the functionally extinct Okinawan population confirm and date a genetic break on the Australian east coast and highlight the need for whole-genome resequencing data from small or isolated dugong populations worldwide for conservation and genetic management.

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Functional or Vestigial? The Genomics of the Pineal Gland in Xenarthra

Cited by 7 publications

References 78 publications

Decay of Skin-Specific Gene Modules in Pangolins

Decay of Skin-Specific Gene Modules in Pangolins

Convergent Decay of Skin-specific Gene Modules in Pangolins

Sirenian genomes illuminate the evolution of fully aquatic species within the mammalian superorder Afrotheria

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